1. Field of the Invention
This invention relates to improvements in motor vehicle fuel vapor recovery systems of the type incorporating canisters that contain adsorbent material capable of absorbing and storing vapors from the vehicle's fuel tank, such vapors resulting mainly from evaporation while the vehicle is idle, or displacement of existing vapors in the tank as it is being filled.
In particular, the invention involves fuel-vapor recovery canisters that are intended to collect fuel vapors from a vent port on a vehicle's fuel tank, store such vapors, and eventually release them and channel them to the vehicle's engine, to be burned.
2. Description of the Related Art Including Information Disclosed Under 37 CFR .sctn..sctn.1.97-1.99
Currently attempts are being made to limit the escape of gasoline vapors from automotive fuel systems, especially the evaporation which occurs while the vehicles are idle. Special fuel tank caps have been used in order to reduce or eliminate fumes that would otherwise escape. In addition, flexible hoods or bushings have been employed in conjunction with the nozzles on the hoses of gasoline pumps, in order to restrict leakage of vapor from the neck of the tank's filler pipe.
In our patent application U.S. Ser. No. 717,515 filed Mar. 28, 1985 in the names of Peter J. Lupoli, Donald J. Mattis, and Robert S. Miller, entitled FUEL VAPOR RECOVERY SYSTEM FOR AUTOMOTIVE VEHICLES, now: U.S. Pat. No. 4,598,686 dated July 8, 1986, as above identified, there is illustrated and described a number of canister constructions adapted to collect and store fuel vapors that originate in the vehicle's fuel tank, and to subsequently purge such vapors and direct them to either the vehicle's carburetor or the engine intake manifold to be burned upon commencement of engine operation. The canisters generally contain granules of carbon or activated charcoal.
All of the canisters disclosed in the above application are of a type which accept vapors from a fuel tank vent port that is connected to the canister through a vapor line, and which rely upon intake of air from the engine compartment to draw off or "purge" stored vapor/condensate after the engine is started. Following such purging of the stored vapor, the adsorbent material in the canister again becomes available for use in collecting and storing subsequently produced vapors.
As presently understood, with canisters of relatively simple geometric shape, such as cylindrical or rectangular units, vapor flow tends to be greatest in certain areas of the canister, namely those adjacent the vapor inlet port, the purge port, and the fresh air inlet port. It is believed that at regions of the canister interior which are adjacent to its walls, flow is more limited. Accordingly the adsorption efficiency of the granules in such regions is reduced, due to their limited exposure to the incoming fuel vapors, as well as their exposure to the air during purging. Stated differently, it is believed that many of the granules do not adsorb and store as much vapor/condensate as others, and thus the overall efficiency of the system is not as high as it might be if an improved flow distribution could be achieved.
In addition, many of the canisters in use are physically large, which presents problems where only limited space is available for automotive accessories of this kind.